Carcass ply producing apparatus, carcass ply producing method and pneumatic tire

ABSTRACT

A carcass ply producing apparatus for producing a carcass ply constituting a carcass layer of a tire comprises  
     a supply head for supplying one or a plurality of ply cords, a head driving mechanism for reciprocating the supply head along a widthwise direction of the carcass ply, a sticking body having a sticking surface to which the ply cord supplied by the supply head is stuck, a sticking body driving mechanism for moving the sticking surface of the sticking body along a longitudinal direction of the carcass ply, and a moving amount controlling mechanism capable of controlling a moving amount of the sticking surface with respect to a moving amount of the supply head, wherein when the ply cord is supplied along the widthwise direction of the carcass ply, a disposition angle of the ply cord with respect to the longitudinal direction can be changed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a carcass ply producingapparatus for producing a carcass ply which constitutes a carcass layerof a tire, a carcass ply producing method using this apparatus, and apneumatic tire constituting the carcass layer by the carcass plyproduced using this apparatus.

[0003] 2. Description of the Related Art

[0004] Currently, a radial tire which is mainstream of a pneumatic tiregenerally comprises a carcass layer in which a portion between a pair ofannular beads is reinforced and a plurality of cords are arranged in aradial direction of the tire (a meridional direction) , and a pluralityof belt layers in which the carcass layer located below a tread isreinforced by hoop effect, and the cords includes a plurality of beltlayers which are inclined in a circumferential direction of the tire.Rigidity of the carcass layer in the radial direction of the tire isgreat, but rigidity there of in the circumferential direction is small,rigidity of the belt layer in the circumferential direction of the tireis great, but rigidity thereof in the radial direction is small.

[0005] Therefore, a local stress is prone to be generated in a belt endwhich is in the vicinity of a boundary between the carcass layer and thebelt layer, which lowers durability of the tire. When the vehiclecorners, it is known that a reaction force is abruptly reduced if thevehicle reaches slip limit, and it is not possible to drive the vehiclein some cases.

[0006] On the other hand, in the case of bias tire existing before theradial tire, rigidity of the tread is insufficient and has no corneringreaction force and thus, motion is inferior. Further, it is known thatshearing distortion is generated in a tire side where flection isgenerated during running because the cords intersect each other, andthat portion is prone to become fatigued and destroyed.

[0007] As a carcass ply producing apparatus for forming the carcasslayer, there is a sticking apparatus of a carcass cord disclosed inJapanese Patent Application Laid-open No.2000-52448 (prior art 1). Thisis an apparatus in which a core which is formed into a doughnut-likeshape as a whole is driven in the circumferential direction, and carcasscord (ply cord) sent from a string-guide is extended in the meridionaldirection of the core and stuck on an outer peripheral surface.

[0008] This apparatus includes a swinging sending-out mechanism whichreciprocates the string-guide provided on a tip end of the arm in themeridional direction of the core along the outer peripheral surface.

[0009] Japanese Patent Application Laid-open No.H.8-207509 (prior art 2)discloses a producing method of a pneumatic tire. According to thismethod, a rubber tape continuously reciprocates in its widthwisedirection in a zigzag manner on a forming drum, bent at a widthwise endof the forming drum and wound around the forming drum, thereby forming acylindrical body (carcass ply).

[0010] Further, Japanese Patent Application Laid-open No.S61-263805(prior art 3) discloses a method in which a carcass ply comprising aplurality of cords arranged straightly is stuck on a forming drum havinga plurality of cylindrical drums and then, the cylindrical drums areinclined through a predetermined angle, thereby partially changing thecord angle of the carcass ply. Outer peripheries of opposite side drumsare pushed by the bands. This prior art 3 discloses a pneumatic tire inwhich a cord of a carcass layer located below a tread is largelyinclined from a meridional direction, two carcass layers in which cordslocated on a tire side are radially arranged are laminated such that theinclined cords intersect with each other, and a reinforcing layer inwhich cords are arranged in its circumferential direction is provided onthe outer peripheral surface of the layer.

[0011] In the case of the apparatus disclosed in the prior art 1,however, the string-guide only reciprocates along the meridionaldirection of the core. Therefore, when the ply cord is supplied in themeridional direction, a disposition angle of the ply cord can notchanged halfway.

[0012] In the case of the carcass ply produced by the prior art 2,although the disposition angle of the ply cord is inclined, thedisposition angle can not be changed halfway in the widthwise direction.

[0013] Whereas, in the case of the prior art 3, the disposition angle ofthe ply cord can be changed halfway in the widthwise direction. However,since the outer peripheries of the opposite side drums are pushed by thebands, there is a drawback that a curvature of the bent portion whosecord angle is changed is prone to become smaller. As disclosed in theprior art 3, even according to a method to apply tension at the time ofvulcanization formation to soften the curve, if flattening becomessmaller to some degree, since the angle variation from the side to thetread is abrupt, it is difficult to soften the curvature of the bentportion. Therefore, a predetermined cord angle can not be realized usingthe prior art 3.

[0014] If the radius of curvature of the bent portion becomes small,there is a problem that a great shearing force is generated between thelayers of the upper layer bent portion and the lower layer bent portionof the carcass layer of the double layered structure and thus, the bentportion is prone to be fatigued and destroyed. Further, since the bentportion is discontinuously changed in cord angle, there are problemsthat prediction ability of the slip limit at the time of cornering islow and improvement in safety is small like the radial tire.

[0015] In the prior art 3, since the outer peripheries of the oppositeside drums are pushed by the band, there is a problem that surplus stepsare required, which complicates the producing step of the carcass ply.There is also a problem that a region of the drum pushed by the band cannot be changed in cord angle.

[0016] The present assignee newly developed a producing method of a plyfor a carcass for forming a carcass layer in which the inclination angleof cord is changed in ever portion of the tire (this is unknown beforethe priority data of the present application). According to this method,even if flattening is small in some degree, carcass layer having smallvariation in cord angle can be formed. However, the following newproblem is caused. That is, if the flattening is small, a width of thetread is relatively wide and thus, if the rigidity of the reinforcinglayer in its circumferential direction provided on an outer periphery ofthe carcass layer is not increased, it is difficult to keep apredetermined shape of the tread of the tire, which lowers the runningperformance.

SUMMARY OF THE INVENTION

[0017] Thereupon, it is an object of the present invention to provide acarcass ply producing apparatus and producing method capable of changingthe disposition angle of a ply cord halfway in its widthwise direction,and capable of realizing a predetermined bending angle.

[0018] It is another object of the invention to provide a pneumatic tirecapable of keeping a predetermined shape in a tire having flattening of70% or less, and capable of enhancing the prediction ability ofcornering to improve safety, and having durability higher than that of aconventional tire.

[0019] To achieve the above objects, the present invention provides acarcass ply producing apparatus for producing a carcass ply constitutinga carcass layer of a tire comprising a supply head for supplying one ora plurality of ply cords, a head driving mechanism for reciprocating thesupply head along a widthwise direction of the carcass ply, a stickingbody having a sticking surface to which the ply cord supplied by thesupply head is stuck, a sticking body driving mechanism for moving thesticking surface of the sticking body along a longitudinal direction ofthe carcass ply, and a moving amount controlling mechanism capable ofcontrolling a moving amount of the sticking surface with respect to amoving amount of the supply head, wherein when the ply cord is suppliedalong the widthwise direction of the carcass ply, a disposition angle ofthe ply cord with respect to the longitudinal direction can be changed.

[0020] Working effects of the carcass ply producing apparatus having theabove structure is as follows:

[0021] (1) First, one or a plurality of ply cords are supplied to asticking surface of a sticking body by a supply head.

[0022] (2) In this case, the supply head reciprocates along a widthwisedirection of the carcass ply. The widthwise direction is a directioncorresponding to the tire meridional direction.

[0023] (3) The sticking surface can move along the longitudinaldirection of the carcass ply. Here, the longitudinal direction is adirection corresponding to a circumferential direction of the tire.

[0024] (4) A moving amount of the sticking surface with respect to amoving amount of the supply head can be controlled.

[0025] For example, as described later, when a carcass layer (carcassply) of a tire having a new structure, while the supply head is movingalong the widthwise direction, the moving amount of the sticking surfacemay be controlled in association with this movement. To control themoving amount of the sticking surface, the moving speed is changedhalfway. With this control, the disposition angle of the carcass cordcan easily be changed.

[0026] As described above, the carcass ply producing apparatus in whichthe disposition angle of the ply cord could be changed halfway in thewidthwise direction of the carcass ply, and a predetermined bendingangle could be realized could be provided.

[0027] In a preferred embodiment of the present invention, the stickingbody is a rotation drum having an outer peripheral surface to which theply cord is stuck.

[0028] With this structure, the ply cord is stuck on the outerperipheral surface of the rotation drum. To change the disposition angleof the ply cord halfway, rotation amount (or rotation speed) of therotation drum is controlled.

[0029] In another preferred embodiment of the invention, the stickingbody is a flat-plate like tray having a surface to which the ply cord isstuck.

[0030] With this structure, the ply cord is stuck on the surface of theflat-plate like tray. To change the disposition angle of the ply cordhalfway, straight moving amount (or moving speed) of the flat-plate liketray is controlled.

[0031] In another preferred embodiment of the invention, the stickingbody is a transfer conveyer having a transfer surface to which the plycord is stuck.

[0032] With this structure, the ply cord is stuck on the surface of thetransfer conveyer. To change the disposition angle of the ply cordhalfway, transfer amount (or transfer speed) of the transfer conveyer iscontrolled. By using the transfer conveyer, the carcass plies cancontinuously be produced.

[0033] To achieve the above object, there is provided a carcass plyproducing method for producing a carcass ply constituting a carcasslayer of a tire comprising

[0034] a step for supplying one or a plurality of ply cords by a supplyhead,

[0035] a step for reciprocating the supply head along a widthwisedirection of the carcass ply,

[0036] a step for sticking the ply cord supplied by the supply head to asticking body having a sticking surface,

[0037] a step for moving the sticking surface of the sticking body alonga longitudinal direction of the carcass ply, and

[0038] a step for controlling a moving amount of the sticking surfacewith respect to a moving amount of the supply head, wherein

[0039] in the step for reciprocating the supply head, a dispositionangle of the ply cord with respect to the longitudinal direction can bechanged.

[0040] The working effect of the producing method of this structure isthe same as the above (1) to (4). With this, the carcass ply producingmethod in which the disposition angle of the ply cord could be changedhalfway in the widthwise direction of the carcass ply, and apredetermined bending angle could be realized could be provided.

[0041] The present invention also provides a pneumatic tire having twoor more carcass layers for reinforcing between a pair of annular beads,and a reinforcing layer having a cord arranged on an outer peripheralsurface of the carcass layer below a tread surface in a circumferentialdirection of a tire, and a flattening of the pneumatic tire being 70% orless, wherein the cord constituting the carcass layers are arrangedsubstantially in a radial direction in a region of the tire from thebead to a position near a tire maximum width, and from that position toa grounding end, an angle with respect to a circumferential direction ofthe tire is gradually changed, and the angle is 20 to 60° with respectto the circumferential direction of the tire in the vicinity of thegrounding end, and the angle is 20 to 50° at the tread surface, thecarcass layers are laminated at angle substantially symmetrical withrespect to a tire equator line, and a tensile modulus per width of thereinforcing layer is 1.2 times or more of the carcass layers.

[0042] Here, the tread surface is a range of inner side of grounding endof each of opposite sides of the tire. A criterion of the tensilemodulus per width of the reinforcing layer is the entire width of thereinforcing layer, and a criterion of the tensile modulus per width ofthe carcass layer is the tread surface, apparent Young's modulus of thecord is measured in accordance with initial tensile resistance of JISL-1017 chemical textile tire cord testing method, the number of cordstrikes per width and a value obtained by multiplying the cord area ofcross section by the number of layers are defined as the tensilemodulus. A criterion of the number of strikes is a cured tire, but thenumber of strikes when material is prepared can be set from inflate rateat the time of forming.

[0043] The working effect of the pneumatic tire of this structure is asfollows.

[0044] According to the pneumatic tire of the invention, the cord anglewith respect to the tire circumferential direction from the tire maximumwidth to the grounding end is gradually changed. Therefore, thereinforcing effect is continuous. Thus, prediction ability of thecornering is high, and safety is enhanced. There is no bent portion inwhich the cord angle is changed discontinuously, and since the cord isdisposed substantially in the radial direction of the tire from the beadto the tire maximum width, peeling off phenomenon between the two layersis less prone to be generated, and stress is less prone to beconcentrated. Further, not only in the tread surface, but also in theoutside shoulder portion, the cords intersect at a small angle toenhance the rigidity in the circumferential direction and thus, kineticability of cornering is enhanced. Since the tensile modulus per width ofthe reinforcing layer is 1.2 times or more of the carcass layer, apredetermined shape of the tread surface can be obtained even if theflattening is small. Further, the rigidity in the circumferentialdirection is enhanced by the reinforcing layer, and rigidity in thelateral direction is also enhanced by the carcass layer in which thecords intersect. Therefore, it is possible to enhance both the kineticability of cornering and safety. As a result, it is possible to providea pneumatic tire in which a predetermined shape can be held in a tirehaving flattening of 70% or less, and the prediction ability of thecornering and safety are improved and durability is higher than that ofthe conventional tire.

[0045] In the above structure, it is preferable that the reinforcinglayer includes a central portion having a width of 45 to 80% of entirewidth of the tread surface located at a center of and below the treadsurface, and opposite sides having tensile modulus per width which islower than that of the central portion. Here, a criterion of the tensilemodulus per width of each portion of the reinforcing layer is the entirewidth of each portion.

[0046] In the case of this preferred embodiment, since the tensilemodulus of the central portion of the reinforcing layer is enhanced ascompared with the side, more desired shape can be held by reinforcingthe central portion of the tread surface which is prone to swell withhigh rigidity.

[0047] It is preferable that the tensile modulus per width of thecentral portion is 1.2 times or more of a tensile modulus per width ofthe side.

[0048] In this case, a desired shape can be held more reliably.

[0049] The present invention also provides a pneumatic tire having twoor more carcass layers for reinforcing between a pair of annular beads,wherein when a region where an angle formed between cords constitutingthe carcass layers and a circumferential direction of the tire is 90±10°is defined as a radial region, and a region where the cords in upper andlower layers intersect while an angle formed between the cords and thecircumferential direction of the tire is 10 to 60° is defined as a biasregion, a region including a position near a tire maximum width includesthe radial region, and the bias region is included in any of a regionbetween the radial region and the bead, and a region between the radialregion and a tire equator line.

[0050] The working effect of the pneumatic tire of this structure is asfollows.

[0051] That is, since the radial region is included in the regionincluding the position near the tire maximum width, riding comfort canbe maintained excellently. Further, since the bias region is included onthe side of the bead in that region, rigidity of the carcass layer canbe enhanced near the bead, steering stability, driving and controlabilities can be enhanced. Since the bias region is also included in thetread of the radial region, rigidity of the carcass layer near theshoulder and tread can be enhanced. As a result, merits of the radialtire and bias tire can properly be used finely in each portion of thetire, it is possible to provide a pneumatic tire in which riding comfortcan be maintained excellently, the rigidity near the bead and theshoulder can be enhanced, and reinforcing structure in that portion isunnecessary or simplified.

[0052] In the above structure, it is preferable that a region having 5to 30% of height from a lower end with respect to height of carcass of atire cross section is mainly the bias region, a region of 40 to 65% ismainly the radial region, and a region of 75 to 95% is mainly the biasregion. Here, mainly bias region means that 80% or more of the entirearea of the designated region is the bias region. The same can beapplied for the radial region. The carcass height of the tire crosssection means that the lower end is the minimum diameter portion of thefolded portion of the carcass layer, and the upper end is the maximumdiameter portion near the tire equator line of the carcass layer (see Hcin FIG. 4).

[0053] In the case of this structure, the bias region and the radialregion are disposed at preferred positions in this order, the aboveeffect can be obtained more reliably.

[0054] It is preferable that a region including the tire equator linefurther include the radial region reinforced by a belt layer, and thebias region is included in any of intermediate region between thatradial region and the radial region near the tire maximum width.

[0055] In the case of this structure, the radial region reinforced bythe belt layer exhibits high rigidity in both the circumferentialdirection and widthwise direction of the tire, and the bias regions onthe opposite sides thereof exhibit appropriate rigidity. Thus, thecontinuity of the rigidity with respect to the radial region near thetire maximum width can be kept. As a result, during the cornering, it ispossible to enhance the prediction ability of the slip limit.

[0056] At that time, it is preferable that a region having 5 to 30% ofheight from a lower end with respect to height of carcass of a tirecross section is mainly the bias region, a region of 40 to 65% is mainlythe radial region, a region of 75 to 95% is mainly the bias region, anda tread is mainly the radial region.

[0057] In this case, the bias region, the radial region, the bias regionand the radial region are disposed at preferred positions in this order,the above effect can be obtained more reliably.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058]FIG. 1 is a partial sectional view showing a pneumatic tireaccording to a first embodiment;

[0059]FIG. 2 are views showing essential portion of the pneumatic tirein FIG. 1, wherein (a) is a front view of partially cut pneumatic tire,and (b) is a plan view thereof;

[0060]FIG. 3 shows one example of a carcass ply, wherein (a) is a planview of a lower layer ply, and (b) is a plan view of an upper layer ply;

[0061]FIG. 4 is a partial sectional view showing a pneumatic tireaccording to a second embodiment;

[0062]FIG. 5 are views showing essential portion of the pneumatic tirein FIG. 4, wherein (a) is a front view of partially cut pneumatic tire,and (b) is a plan view thereof;

[0063]FIG. 6 shows one example of a carcass ply, wherein (a) is a planview of a lower layer ply, and (b) is a plan view of an upper layer ply;

[0064]FIG. 7 is a plan view showing another cord arrangement of thecarcass ply;

[0065]FIG. 8 shows a structure of a carcass ply producing apparatusaccording to the first embodiment;

[0066]FIG. 9 is a front view of a supply head;

[0067]FIG. 10 is a side view of the supply head;

[0068]FIG. 11 shows a structure of a carcass ply producing apparatusaccording to the second embodiment; and

[0069]FIG. 12 shows a structure of a carcass ply producing apparatusaccording to a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0070] Preferred embodiments of a carcass ply producing apparatus and apneumatic tire of the present invention will be explained using thedrawings. First, a pneumatic tire constituting a carcass layer by acarcass ply produced by the producing apparatus will be explained. FIG.1 is a partial sectional view showing a pneumatic tire according to afirst embodiment. FIG. 2(a) is a front view of partially cut pneumatictire, and FIG. 2(b) is a plan view thereof.

Structure of Pneumatic Tire (First Embodiment)

[0071] As shown in FIG. 1, the pneumatic tire comprises a carcass layer5 having two or more layers for reinforcing between a pair of annularbeads 1 a, and a reinforcing layer 6 provided below a tread surface Tron an outer peripheral surface of the carcass layer 5. This embodimentshows an example in which the carcass layer 5 comprises two layers.

[0072] In the present invention, flattening showing, with percentage, avalue obtained by dividing a height H of cross section of the tire by atire maximum width W is 70% or less. As the flattening is reduced to 65%or less or 60% or less, the present invention having the above effectsbecomes more effective. That is, it is possible to enhance theprediction of the cornering to improve the safety, and to enhance thecornering performance by flattening the tire.

[0073] As shown in FIG. 2, the present embodiment is characterized inthat a cord constituting the carcass layer 5 is disposed at differentangle depending upon a portion of the tire. More specifically, at aregion S1 from a bead 1 a to a position PW near a tire maximum width W,the cord is disposed substantially in a radial direction of the tire(e.g. θs=90°), at a region S2 from the position PW to a ground end PT,the angle (cord angle, hereinafter) with respect to a circumferentialdirection of the tire is gradually changed, at a shoulder portion Shnear the ground end PT, the cord angle is 20 to 60°, and at a treadsurface Tr between opposite ground end PT, the cord angle is 20 to 50°(e.g., θt=35°). Preferably, the cord angle at the shoulder Sh is 20 to50°, and the cord angle at the tread surface Tr is 20 to 40°.

[0074] If the cord angle at the tread surface Tr exceeds 50°, thecarcass layer 5 at the tread surface Tr is prone to be extended in theradial direction RD of the tire and it is difficult to maintain itsshape. If the cord angle at the treat Tr becomes smaller than 20°,although the rigidity in the circumferential direction at the treat Tris increased, rigidity in its widthwise direction becomes small andthus, the cornering performance is deteriorated, and it is difficult togradually varying the angle from the ground end PT to the bead 1.

[0075] The lower layer carcass layer 5 a and an upper layer carcasslayer 5 b are laminated such that the cords are disposed atsubstantially symmetrical angle with respect to a tire equator line CL.Opposite ends of the carcass layer 5 are folded back outward at a bead 1a, a bead filler 1 b having high rubber hardness is disposed between thefolded portion and a body of the carcass layer 5, and a bead 1 isformed. Like a common tire, a side wall rubber 2 a, an inner linerrubber 3, a tread rubber 4 and the like are disposed on outer side ofthe carcass layer 5. Predetermined patterns are formed on an outerperipheral surface of the tread rubber 4.

[0076] A reinforcing layer 6 is a layer in which cords are arranged in atire circumferential direction (i.e., direction which is parallel to thetire equator line CL), and is disposed at a position below the treadsurface Tr of the outer peripheral surface of the outermost carcasslayer 5 b. It is unnecessary that the reinforcing layer 6 coincides witha width of the tread surface Tr, and usually has a width in a rangeexceeding a width of the tread surface Tr. More specifically, it ispreferable that the width of the reinforcing layer 6 is 1.0 to 1.3 timesof the width of the tread surface Tr.

[0077] Tensile modulus per entire width of the reinforcing layer 6 is1.2 times or more of tensile modulus (sum of all the layers) of thecarcass layer 5 of the treat Tr, and is preferably 1.5 to 6 times. Ifthe tensile modulus exceeds 6 times, the tire is inferior in terms ofprocessing aspect or producing aspect. The tensile modulus per width ofthe reinforcing layer 6 can be adjusted by the number of strike of thecord, thickness and material of the cord, and component of fiber, andprocessing condition of the fiber. The same is applied to the carcasslayer 5 also.

[0078] Examples of material of the cord constituting the carcass layer 5are organic fiber such as polyester, polyamide and polyaramide or steeland the like. Examples of material of the cord constituting thereinforcing layer 6 are also organic fiber such as polyester, polyamideand polyaramide or steel and the like. In the present invention, sinceit is unnecessary to provide a plurality of belt layers unlike theconventional radial tire, weight of the tire can be lowered. Further,since the reinforcing layer 6 reinforces the biased carcass layer 5,bending rigidity of that portion is enhanced and thus, the cord of thereinforcing layer 6 can be constituted by the organic fiber to furtherreduce the weight. It is possible to enhance both the corneringperformance and safety.

[0079] Preferably, the reinforcing layer 6 is provided at its centralposition below the tread surface Tr with a central portion 6 a disposedin a range Tc of 45 to 80% of the entire width of the tread surface Tr,and opposite side portions 6 b having lower tensile modulus per width ofthe central portion 6 a. This embodiment shows the example which thenumber of strikes of the central portion 6 a is increased than that ofthe side portions 6 b. The reinforcing layer 6 is usually formed in sucha manner that after shaping, a ribbon-like reinforcing layer comprisingone or small number of cords are spirally wound so as to remove cutportions of the cords. It is possible to increase the number of strikesof the central portion 6 a by changing the winding pitch.

[0080] In the present invention, it is preferable that the tensilemodulus per width of the central portion 6 a is 1.2 time or more of thetensile modulus per width of the side portion 6 b. More preferably, thetensile modules per width of a portion from a center (position on thetire equator line CL) of the reinforcing layer 6 to the opposite ends isgradually reduced. This can be done also by gradually increasing thewinding pitch.

[0081] The pneumatic tire of the present invention can be produced inthe same manner as that of a common pneumatic tire except that carcassplies 8 a and 8 b in which cord angle is partially changed to a positionin the widthwise direction are used as shown in FIG. 3. The carcassplies 8 a and 8 b are laminated cylindrically so that cords are disposedsubstantially symmetrically with respect to the center line, a bead isdisposed for example and then, a turn up bladder is inserted, the tireis shaped into toroidal shape and then, the reinforcing layer 6 and thetread are formed.

Modification of First Embodiment

[0082] (1) In the first embodiment, two carcass layers are provided. Thenumber of the layers may be even number such as four. In such a casealso, it is preferable that the pair of carcass layers are laminatedsuch that the cords are disposed at substantially symmetrical angle withrespect to a tire equator line, and the cords of the carcass layerslaminated in the same direction are disposed in the same direction attheir positions.

[0083] (2) In the first embodiment, one reinforcing layer in thecircumferential direction is provided, and the tensile modulus per widthis enhanced by changing the number of strikes at the central portion.Alternatively, the tensile modulus per width may be enhanced byproviding two reinforcing layers of central portion. Two or morereinforcing layers may be provided.

Structure of Pneumatic Tire (Second Embodiment)

[0084] As shown in FIG. 4, a pneumatic tire of the second embodimentincludes two or more carcass layers 5 for reinforcing between a pair ofannular beads 1 a. In this embodiment, the carcass layer 5 comprises anupper layer 5 b and a lower layer 5 a. In this invention, a region inwhich an angle θs formed between a cord constituting the carcass layerand a tire circumferential direction PD is 90±10° is defined as a radialregion RR, and a region in which the cords of the upper and lower layersintersect with each other when the angle θs (“cord angle” in some caseshereinafter) between the cord and the tire circumferential direction PDis 10 to 60° (absolute value) is defined as a bias region BR. The cordangle θs of each of the upper and lower layers may be slightly varied atthe intersection.

[0085] As shown in FIG. 5, the present invention is characterized inthat a region including a position near the tire maximum width positionPW includes the radial region RR, any of region between the radialregion RR and the bead 1 a, and any region between the radial region RRand the tire equator line CL includes the bias region BR. In thisembodiment, a region including the tire equator line CL further includesa radial region RR reinforced by a belt layer 6, and any region locatedintermediate portion between the radial region RR and another radialregion near the tire maximum width PW includes the bias region BR.

[0086] More specifically, it is preferable that a region in which aheight ratio of the tire cross section with respect to carcass height Hcfrom the lower end is 5 to 30% is the bias region BR, a region of 40 to65% is mainly a radial region RR, a region of 75 to 95% is mainly thebias region BR, and the tread surface Tr is mainly the radial region RR.It is preferable that an intermediate region which corresponds nothingis provided between the radial region RR and the bias region BR so thatthe cord angle θs is gently changed.

[0087] At that time, it is preferable that a region in which a heightratio of the tire cross section with respect to carcass height Hc fromthe lower end is 75 to 95% corresponds to the shoulder portion Sh, andthe bias region BR is disposed in this portion. If an end side of alayer having the maximum width (lower layer 6 a in the illustratedexample) among the plurality of belt layers 6 is disposed on this biasregion BR, stress is less prone to be generated in the vicinity of theend of the belt layer 6 as compared with a case in which the end side isdisposed on the radial region RR, and continuity of rigidity withrespect to the radial region RR in the vicinity of the tire maximumwidth becomes excellent.

[0088] Although the upper layer 6 b and the lower layer 6 a constitutethe belt layer 6 in this embodiment, it is preferable that the angle ofthe cord constituting each layer with respect to the tire equator lineCL is 10 to 35°, and more preferably, 15 to 25°. A fiber reinforcinglayer in which a cord is disposed in the circumferential direction maybe provided on an upper surface of the upper layer 6 b.

[0089] As a material of the cord constituting the belt layer 6, any ofmaterial which is used for conventional belt layer 6 such as steel ororganic fiber including polyester may be used. Examples of cord materialconstituting the fiber reinforcing layer are organic fiber such aspolyester, polyamide and polyaramide.

[0090] In order to enhance the rigidity in the vicinity of the bead 1 aand to enhance the operation stability, driving and braking performance,it is preferable that the cord angle θs of the bias region BR disposednear the bead 1 a is 10 to 60°, and more preferably, 20 to 50°. As aresult, it is possible to reduce the bead filler and reinforcing plyaround the bead.

[0091] In order to disperse the stress and to enhance the continuity ofrigidity, it is preferable that the cord angle θs of the bias region BRdisposed near the shoulder portion Sh is 10 to 60°, and more preferably,20 to 50°. As a result, it is possible to reduce the reinforcing plyaround the belt end.

[0092] The lower carcass layer 5 a and the upper carcass layer 5 b arelaminated such that cords are disposed substantially symmetrically withrespect to the tire equator line CL. Examples of material of the cordconstituting the carcass layer 5 are organic fiber such as polyester,polyamide and polyaramide or steel and the like.

[0093] The pneumatic tire of the present invention has substantially thesame structure as that of a usual radial tire except that the cord angleθs of the carcass layer 5 is partially changed. That is, as shown inFIG. 4, opposite ends of the carcass layer 5 are folded back outward atthe bead 1 a, a bead filler 1 b having high rubber hardness is disposedbetween the folded portion and a body of the carcass layer 5, and a bead1 is formed. Like a common tire, a side wall rubber 2 a is disposed onouter side of the carcass layer 5, and an inner liner rubber 3 isdisposed on inner side of the carcass layer 5, and a tread rubber 4 andthe like are disposed on outer side of the belt layer 6. Predeterminedpatterns are formed on an outer peripheral surface of the tread rubber4.

[0094] In the present invention, flattening showing, with percentage, avalue obtained by dividing a height H of cross section of the tire by atire maximum width W is 70% or less. As the flattening is reduced to 65%or less or 60% or less, it is possible to enhance the prediction of thecornering to improve the safety, and to enhance the corneringperformance by flattening the tire.

[0095] The pneumatic tire of the present invention can be produced inthe same manner as that of a common pneumatic tire except that carcassplies 8 a and 8 b in which cord angle is partially changed to a positionin the widthwise direction are used as shown in FIG. 6. The carcassplies 8 a and 8 b are laminated cylindrically so that cords are disposedsubstantially symmetrically with respect to the center line, a bead isdisposed for example and then, a turn up bladder is inserted, the tireis shaped into toroidal shape and then, the belt layer 6 is formed by anormal method.

Modification of Second Embodiment

[0096] (1) In the second embodiment, the bias region, the radial region,the bias region and the radial region are disposed in this order betweenthe bead to the tire equator line. Alternatively, the bias region, theradial region and the bias region may be disposed in this order betweenthe bead and the shoulder portion, and the bias region may be disposedalso in the tread. At that time, it is preferable that a region in whicha height ratio of the tire cross section with respect to carcass heightHc from the lower end is 5 to 30% is the bias region, a region of 40 to65% is mainly a radial region, a region of 75 to 95% is mainly the biasregion.

[0097] In the above case, it is preferable that the belt layer is notprovided on the outer peripheral surface of the bias region of thetread, and a reinforcing layer in which the cord is arranged in the tirecircumferential direction is provided. It is preferable that thisreinforcing layer has tensile modulus per width of 1.2 time or more ofthat of the carcass layer. It is preferable that the reinforcing layerincludes a central portion disposed in a range of 45 to 80% of theentire tread surface in a central position below the tread surface, andopposite sides having tensile modulus per width lower than that of thecentral portion. It is preferable that the tensile modulus per width ofthe central portion is 1.2 times or more of the tensile modulus perwidth of the side.

[0098] Here, the tread surface is a range of inner side of grounding endof each of opposite sides of the tire. A criterion of the tensilemodulus per width of the reinforcing layer is the entire width of thereinforcing layer, and a criterion of the tensile modulus per width ofthe carcass layer is the tread surface, apparent Young's modulus of thecord is measured in accordance with initial tensile resistance of JISL-1017 chemical textile tire cord testing method, the number of cordstrikes per width and a value obtained by multiplying the cord area ofcross section by the number of layers are defined as the tensilemodulus. A criterion of the number of strikes is a cured tire, but thenumber of strikes when material is prepared can be set from inflate rateat the time of forming.

[0099] (2) In the second embodiment, the cords constituting the carcasslayer are arranged as shown in FIG. 6, but they may be arrangedvariously as shown in FIG. 7. In FIG. 7, only one unit C of the cords ofthe carcass ply of each of the upper layer and lower layer is shown.

[0100]FIGS. 7A to 7B show line symmetric arrangement with respect to thetire equator line CL. FIGS. 7C to 7D show symmetric arrangement withrespect to a point at the intersection between the cord and the tireequator line CL. In the above modification (1), for example, a carcassply having cord arrangement shown in FIG. 7(d) can be used.

[0101] (3) In the second embodiment, two carcass layers are provided.The number of the layers may be even number such as four. In such a casealso, it is preferable that the pair of carcass layers are laminatedsuch that the cords are disposed at substantially symmetrical angle withrespect to a tire equator line, and the cords of the carcass layerslaminated in the same direction are disposed in the same direction attheir positions.

[0102] (4) In the second embodiment, arrangement of the radial regionand the bias region for the body portion of the carcass layer isexplained. However, in the folded portion of the carcass layer, any ofthe radial region, the bias region and an intermediate region whichcorresponds nothing may be disposed. In the present invention, it ispreferable that the bias region is disposed also in the folded portionof the carcass layer to further enhance the rigidity of the carcasslayer near the bead.

[0103] At that time, the folded portion may be formed without changingthe cord angle of the body of the carcass layer disposed near the bead(see FIG. 7), and only the carcass layer disposed around the bead(portion circumscribing the bead) may be set as the radial region. Thepreferable cord angle of the bias region in the folded portion is thesame as the cord angle of the body.

Structure of Carcass Ply Producing Apparatus (First Embodiment)

[0104] A structure of a first embodiment of a carcass ply producingapparatus for producing the carcass plies 8 a and 8 b shown in FIGS. 3and 6 with reference to FIGS. 8 and 9.

[0105] As shown in FIG. 8, the carcass ply producing apparatus comprisesa bobbin 11 around which a cord material 10 is wound, a covering rubberextrusion machine 12 for covering the cord material 10 sent from thebobbin 11 with covering rubber, roller group 13, a shock-absorbingportion 14 including shock-absorbing rollers 14 a, a guide roller 15, ahead driving mechanism 16 for supplying the a cord 10 a (ply cord) alonga widthwise direction of the carcass ply, and a flat-plate like tray 17(corresponding to sticking body) to which the cord is stuck. A stickingsurface of the tray 17 is formed of a material capable of sticking thecord such as rubber and aluminum. The apparatus further comprises acontrolling apparatus 20 the carcass ply producing apparatus. Thecontrolling apparatus 20 comprises a tray driving section 20 a fordriving the flat-plate like tray 17 and a head driving section 20 b fordriving a supply head 19. The head driving mechanism 16 includes thesupply head 19 and a head guide section 18.

[0106] By allowing the cord material 10 sent from the bobbin 11 to passthrough a base 12 a of the covering rubber extrusion machine 12, uncuredrubber is covered. The cord 10 a covered with rubber is sent between theshock-absorbing rollers 14 a of the shock-absorbing portion 14 and isloosened. This shock-absorbing portion 14 is provided for adjusting theprocessing speed before and after the above operation.

[0107] A tip end of the cord 10 a covered with rubber is supplied alongthe widthwise direction (X direction: meridional direction of tire) ofthe carcass ply 8 a by the supply head 19 of the head driving mechanism16. Details of the supply head 19 are shown in FIGS. 9 and 10. FIG. 9 isa front view of the supply head 19, and FIG. 10 is a side view of thesupply head.

[0108] The supply head 19 includes a first head section 191 and a secondhead section 192. The first head section 191 includes supply rollers 191a, 191 b and a pressure roller 191 c. Similarly, the second head section192 includes supply rollers 192 a, 192 b and a pressure roller 192 c.Although FIG. 10 shows only the side of the second head section 192, therollers 192 a, 192 b, 192 c are supported on a first supporting body 193by a bearing 197 and a bolt 196. The first supporting body 193 is fixedto a second supporting body 194 by means of bolts 198. The secondsupporting body 194 can be driven vertically by a cylinder 195. Thefirst head section 191 also has the same structure. A mechanism forvertically moves the second supporting body 194 may employ a motor orcam.

[0109] In FIG. 9, the cord 10 a is supplied downward from above. Thecord 10 a is sandwiched between the supply rollers 191 a and 192 a andthe pressure rollers 191 b and 192 b and supplied, and stuck to thesticking surface of the tray 17 by the pressure rollers 191 b and 192 b.In FIG. 9, the supply head 19 is moving from left side to the rightside. In this case, the cord 10 a is pushed by the pressure rollers 191b and 191 c on the side of the first head section 191, and the secondhead section 192 floats up from the sticking surface slightly. On theother hand, when the supply head 19 moves from the right side to theleft wide, the cord 10 a is pushed by the pressure rollers 192 b and 192c on the side of the second head section 192.

[0110] The supply head 19 can reciprocate along the head guide section18, and for example, a known linear guide mechanism can be used. Thetray 17 can also move along the longitudinal direction (Y direction:circumferential direction of the tire) of the carcass ply. A knownlinear guide mechanism can be used as a mechanism (corresponding to asticking body driving mechanism) for moving the tray 17 in the Ydirection.

[0111] The supply head 19 and the tray 17 are driven based on commandsfrom the control apparatus 20 (corresponding to a moving amount controlmechanism), but it is possible to control the moving amount of the tray17 with respect to the moving amount of the supply head 19. This controlis carried out based on a control program stored in the controlapparatus 20. By carrying out such a control, when the cord 10 a issupplied along the widthwise direction of the carcass ply, thedisposition angle of the cord with respect to the longitudinal directionof the carcass ply can be changed.

[0112] For example, when the carcass ply as shown in FIG. 3 is produced,the tray 17 is controlled during forward movement of the supply head 19in the following manner. It is assumed that the supply head 19 moves ata constant speed.

[0113] (1) right ply end ˜ near tire maximum width: tray is stopped.

[0114] (2) near tire maximum width ˜ right shoulder portion: tray moveswhile gently accelerating.

[0115] (3) right shoulder portion ˜ left shoulder portion: tray moves ata constant speed.

[0116] (4) left shoulder portion ˜ near tire maximum width: tray moveswhile gently decelerating.

[0117] (5) near tire maximum width ˜ left ply end: tray is stopped.

[0118] During the forward movement of the supply head 19, the tray 17 iscontrolled in the above manner. During a backward movement of the supplyhead 19, the tray 17 is moved by a distance corresponding to the numberof ply cords (in the example in FIG. 9, one ply cord because one cord issupplied), the above (1) to (5) operations are carried out in thereversed order.

[0119] As shown in FIG. 3, when the carcass layer is of a double layerstructure comprising the carcass plies 8 a and 8 b, a first layercarcass ply is produced by controlling the tray 17 in accordance withthe above (1) to (5) operations, and the tray 17 is controlled such thata second layer carcass ply moves in a direction opposite from the above(1) to (5) operations. The moving speed of the supply head 19 isconstant in both forward and backward movements.

[0120] If a carcass ply corresponding to one tire is produced on thetray 17, the cord 10 a is cut, a new tray 17 is placed, the sameoperations are carried out, thereby producing a next carcass ply. Byrepeating this procedure, necessary number of carcass plies areproduced. The produced carcass plies on the tray 17 are supplied to aforming machine one by one, thereby producing a tire using a knownmethod.

[0121] It is preferable that the reinforcing layer 6 is formed byspirally winding one or a small number of cords around the shapedobject. Using the cord covered with rubber as in the above manner, theguide of the cord is moved in the widthwise direction while rotating theshaped object, thereby spirally winding the cord. By changing the movingspeed of the guide at that time, the number of strikes at the widthwisedirection can be changed.

[0122] In order to obtain a predetermined tire shape and a predeterminedcord angle at each portion, it is preferable to appropriately adjust thecord angle when the carcass plies 8 a and 8 b are produced. In the caseof the bias tire, a relation between a cord angle in the ply state and acord angle after the tire is formed can be calculated by the followingknown relational equation (approximate expression) , and this relationalequation can also be applied in the present invention. If “Ad” is usedas variable and “R” of the corresponding portion is determined, “A” canbe obtained.

Rd cos A=R cos Ad

[0123] Here, “Rd” represents a radius of a drum, “Ad” represents a cordangle with respect to a circumferential direction on the drum, “R”represents a radius corresponding to a position of the cord after thetire is formed, and “A” represents a cord angle with respect to thecircumferential direction after the tire is formed.

Structure of Carcass Ply Producing Apparatus (Second Embodiment)

[0124] A structure of a second embodiment of a carcass ply producingapparatus will be explained with reference to FIG. 11. Members havingthe same functions as those in the first embodiment are designated withthe same numbers, and explanation thereof is omitted.

[0125] The second embodiment is different from the first embodiment inthat the sticking body comprises a rotation drum 21. An outer peripheralsurface of the rotation drum 21 functions as a sticking surface of thecord. The outer peripheral surface is made of rubber or aluminum. Whenthe carcass ply shown in FIG. 3 is produced, control of the rotationdrum 21 during the forward movement of the supply head 19 is as follows.The rotation drum 21 is rotated and driven by a motor (not shown) (whichcorresponds to a sticking body driving mechanism).

[0126] (1) right ply end ˜ near tire maximum width: rotation drum isstopped.

[0127] (2) near tire maximum width ˜ right shoulder portion: rotationdrum moves while gently accelerating.

[0128] (3) right shoulder portion ˜ left shoulder portion: rotation drummoves at a constant speed.

[0129] (4) left shoulder portion ˜ near tire maximum width: rotationdrum moves while gently decelerating.

[0130] (5) near tire maximum width ˜ left ply end: rotation drum isstopped.

[0131] During the forward movement of the supply head 19, the rotationdrum 21 is controlled in the above manner. During a backward movement ofthe supply head 19, the rotation drum 21 is moved by a distancecorresponding to the number of ply cords (in the example in FIG. 9, oneply cord because one cord is supplied) , the above (1) to (5) operationsare carried out in the reversed order. By repeating this procedure onecycle of the rotation drum 21, the carcass ply can be produced. When thecarcass layer is of a double layer structure, it can be produced as inthe first embodiment.

Structure of Carcass Ply Producing Apparatus (Third Embodiment)

[0132] A structure of a third embodiment of a carcass ply producingapparatus of the third embodiment will be explained with reference toFIG. 12. Members having the same functions as those in the firstembodiment are designated with the same numbers, and explanation thereofis omitted.

[0133] The third embodiment is different from the first embodiment inthat the sticking body comprises a transfer conveyer 22. A transfersurface of the transfer conveyer 22 functions as a sticking surface ofthe cord. The transfer surface is made of, for example, rubber. When thecarcass ply shown in FIG. 3 is produced, control of the transferconveyer 22 during the forward and backward movements of the supply head19 is the same as in the case of the first embodiment. The transferconveyer 22 is driven by a motor (not shown) (which corresponds to asticking body driving mechanism).

[0134] The produced carcass plies are wound around the bobbin 24together with a cloth 23. When the carcass layer is of the double layerstructure, a first layer can be produced in the above manner, and asecond layer can be produced by moving the transfer conveyer 22 in theopposite direction from that of the first layer.

Another Embodiment

[0135] (1) In the present embodiment, one ply cord is supplied, but aplurality of cords may also be supplied.

[0136] (2) The producing apparatus of the present invention is suitablefor producing the carcass ply shown in FIG. 3 or 6, but the carcass plyto be produced is not limited to one shown in FIG. 3 or 6. It ispossible to produce a carcass ply whose disposition angle of the cord isnot changed. That is, it is possible to produce various carcass plies.

What is claimed is:
 1. A carcass ply producing apparatus for producing acarcass ply constituting a carcass layer of a tire comprising a supplyhead for supplying one or a plurality of ply cords, a head drivingmechanism for reciprocating said supply head along a widthwise directionof said carcass ply, a sticking body having a sticking surface to whichsaid ply cord supplied by said supply head is stuck, a sticking bodydriving mechanism for moving said sticking surface of said sticking bodyalong a longitudinal direction of said carcass ply, and a moving amountcontrolling mechanism capable of controlling a moving amount of saidsticking surface with respect to a moving amount of said supply head,wherein when said ply cord is supplied along the widthwise direction ofsaid carcass ply, a disposition angle of said ply cord with respect tosaid longitudinal direction can be changed.
 2. The carcass ply producingapparatus according to claim 1, wherein said sticking body is a rotationdrum having an outer peripheral surface to which said ply cord is stuck.3. The carcass ply producing apparatus according to claim 1, whereinsaid sticking body is a flat-plate like tray having a surface to whichsaid ply cord is stuck.
 4. The carcass ply producing apparatus accordingto claim 1, wherein said sticking body is a transfer conveyer having atransfer surface to which said ply cord is stuck.
 5. A carcass plyproducing method for producing a carcass ply constituting a carcasslayer of a tire comprising a step for supplying one or a plurality ofply cords by a supply head, a step for reciprocating said supply headalong a widthwise direction of said carcass ply, a step for stickingsaid ply cord supplied by said supply head to a sticking body having asticking surface, a step for moving said sticking surface of saidsticking body along a longitudinal direction of said carcass ply, and astep for controlling a moving amount of said sticking surface withrespect to a moving amount of said supply head, wherein in said step forreciprocating said supply head, a disposition angle of said ply cordwith respect to said longitudinal direction can be changed.
 6. Thecarcass ply producing method according to claim 5, wherein said stickingbody is a rotation drum having an outer peripheral surface to which saidply cord is stuck.
 7. The carcass ply producing method according toclaim 5, wherein said sticking body is a flat-plate like tray having asurface to which said ply cord is stuck.
 8. The carcass ply producingmethod according to claim 5, wherein said sticking body is a transferconveyer having a transfer surface to which said ply cord is stuck.
 9. Apneumatic tire having two or more carcass layers for reinforcing betweena pair of annular beads, and a reinforcing layer having a cord arrangedon an outer peripheral surface of said carcass layer below a treadsurface in a circumferential direction of a tire, and a flattening ofsaid pneumatic tire being 70% or less, wherein said cord constitutingsaid carcass layers are arranged substantially in a radial direction ina region of the tire from said bead to a position near a tire maximumwidth, and from that position to a grounding end, an angle with respectto a circumferential direction of the tire is gradually changed, and theangle is 20 to 60° with respect to the circumferential direction of thetire in the vicinity of said grounding end, and the angle is 20 to 50°at the tread surface, said carcass layers are laminated at anglesubstantially symmetrical with respect to a tire equator line, and atensile modulus per width of said reinforcing layer is 1.2 times or moreof said carcass layers.
 10. The pneumatic tire according to claim 9,wherein said reinforcing layer includes a central portion having a widthof 45 to 80% of entire width of said tread surface located at a centerof and below said tread surface, and opposite sides having tensilemodulus per width which is lower than that of said central portion. 11.The pneumatic tire according to claim 10, wherein the tensile modulusper width of said central portion is 1.2 times or more of a tensilemodulus per width of said side.
 12. A pneumatic tire having two or morecarcass layers for reinforcing between a pair of annular beads, whereinwhen a region where an angle formed between cords constituting saidcarcass layers and a circumferential direction of said tire is 90±10° isdefined as a radial region, and a region where said cords in upper andlower layers intersect while an angle formed between said cords and thecircumferential direction of the tire is 10 to 60° is defined as a biasregion, a region including a position near a tire maximum width includessaid radial region, and said bias region is included in any of a regionbetween said radial region and said bead, and a region between saidradial region and a tire equator line.
 13. The pneumatic tire accordingto claim 12, wherein a region having 5 to 30% of height from a lower endwith respect to height of carcass of a tire cross section is mainly saidbias region, a region of 40 to 65% is mainly said radial region, and aregion of 75 to 95% is mainly said bias region.
 14. The pneumatic tireaccording to claim 12, wherein a region including the tire equator linefurther include said radial region reinforced by a belt layer, and saidbias region is included in any of intermediate region between thatradial region and said radial region near the tire maximum width. 15.The pneumatic tire according to claim 14, wherein a region having 5 to30% of height from a lower end with respect to height of carcass of atire cross section is mainly said bias region, a region of 40 to 65% ismainly said radial region, a region of 75 to 95% is mainly said biasregion, and a tread is mainly said radial region.